Mesoporous silica nanoparticles (MCM-41) coated PEGylated chitosan as a pH-Responsive nanocarrier for triggered release of erythromycin [electronic resource]

, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; 2014, Volume 63, Issue 13, Pages 692-697 Pourjavadi, A. (Ali) ; Mazaheri Tehrani, Zahra ; Sharif University of Technology

Abstract

A pH-responsive drug delivery system based on core shell structure of mesoporous silica nanoparticle (MSN) and chitosan-PEG copolymer was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM) techniques. In order to improve compatibility MSN and drug, mesoporous nanosilica was modified by 3-aminopropyl triethoxysilane. The release of erythromycin (a macrolide antibiotic) as a model drug was investigated in two pHs, 7.4 and 5.5

Elastic-plastic modeling of the hardening materials based on an Eulerian strain tensor and a proper corotational rate

, Article 2005 ASME Pressure Vessels and Piping Conference, PVP2005, Denver, CO, 17 July 2005 through 21 July 2005 ; Volume 2 , 2005 , Pages 201-206 ; 0277027X (ISSN) Naghdabadi, R ; Ghavam, K ; Sharif University of Technology

2005

Abstract

In this paper a model for analyzing elastic-plastic kinematic hardening materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian strain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be...

Some advantages of the elliptic weight function for the element free galerkin method

, Article 2005 ASME Pressure Vessels and Piping Conference, PVP2005, Denver, CO, 17 July 2005 through 21 July 2005 ; Volume 2 , 2005 , Pages 459-464 ; 0277027X (ISSN) Naghdabadi, R ; Asghari, M ; Sharif University of Technology

2005

Abstract

In this paper, an anisotropic weight function in the elliptic form is introduced for the Element Free Galerkin Method (EFGM). In the circular (isotropic) weight function, each node has one characteristic parameter that determines its domain of influence. In the elliptic weight function, each node has three characteristic parameters that are major influence radius, minor influence radius and the direction of the major influence. Using the elliptic weight function each point of the domain may be affected by a less number of nodes in certain conditions. Thus, the computational cost of the method is decreased. In addition, the dependency of the solution on the method that is used for the...

Large elastic-plastic deformation analysis of rectangular plates

, Article New and Emerging Computational Methods: Applications to Fracture, Damage and Reliability (2002 ASME Prssure Vessels and Piping Conference), Vancouver, BC, 5 August 2002 through 9 August 2002 ; Volume 438 , 2002 , Pages 153-159 ; 0277027X (ISSN) Naghdabadi, R ; Shahi, M ; Sharif University of Technology

2002

Abstract

The purpose of this paper is to find a fast and simple solution for the large deformation of rectangular plates considering elastic-plastic behavior. This analysis contains material and geometric nonlinearities. For geometric nonlinearity the concept of load analogy is used. In this method the effect of nonlinear terms of lateral displacement is considered as suitable combination of additional fictitious lateral load, edge moment and in-plane forces acting on the plate. Variable Material Property (V.M.P.) method has been used for analysis of material nonlinearity. In this method, the basic relations maintain the form of stress-strain elastic formula, while material properties are modified to...

Investigating Effect of Nano Ceramic Coating of Combustion Chamber on the Performance of Internal Combustion Engines

, M.Sc. Thesis Sharif University of Technology Sharifi, Masoud (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Thermal barrier coatings (TBCs) are used for increasing the efficiency and reducing pollutants of internal combustion engines (ICEs). In this paper, an optimization framework is developed in order to obtain the optimal dimensions for conventional coat, and the optimal dimensions and material property for functionally graded (FG) coat of a partially coated piston. A thermo mechanical analysis is investigated for Nano coat by finite element method. The conventional and Nano coats are made of MgZrO_3 as the insulating ceramic overlay and NiCrAl as the metallic bond-coat. The properties of the FG coat is assumed to vary according to power law through the thickness. For all tree conventional, FG...

Thermoelastic Analysis of Thick-walled FG Cylinders Using the Strain Gradient Elasticity

, M.Sc. Thesis Sharif University of Technology Sadeghi, Hossein (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

There are experimental observations that show material response in micro-scale is dependent on some other parameters rather than Lame parameters. Strain gradient elasticity has been recently developed to take into account this characteristic of materials response. In strain gradient elasticity, characteristic length parameters enter the constitutive equations through the elastic strain energy density function. The elastic strain energy density function is assumed to be a function of the gradient of strain tensor in addition to the strain tensor. In this way, new material constant (characteristic length parameters) are introduced and entered into the constitutive equations. In recent years,...

An Analytical Solution for the Polymeric Liner Collapse in Hyperbaric type IV Hydrogen Storage Vessels

, M.Sc. Thesis Sharif University of Technology Alizadeh, Mostafa (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Type IV high pressure vessels are composite vessels with a polymeric liner, which are the best choice for storing hydrogen in hydrogen vehicles. The defect of these vessels is the penetration of light hydrogen molecules in the polymeric liner and the composite part. When depressurization the vessel, these molecules cannot release from the polymeric liner and the composite part according to the emptying rate of the vessel. Thus, concentration of the hydrogen molecules in the polymeric liner becomes more than inside the vessel which leads to a pressure difference between the two sides of the polymeric liner that causes the liner collapse. In this research, the partial differential equation for...

Modeling Magneto-Mechanical Behavior of Porous Magnetic Gel at Large Deformations in External Magnetic Field

, M.Sc. Thesis Sharif University of Technology Rezaei, Shayan (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Magnetic gels and ferrogels are smart composite materials made by combining magnetic particles in a polymer matrix. These materials have been considered due to their special properties such as deformation and change of mechanical properties in the presence of external magnetic field. Having polymer properties along with the magnetic properties of metals, have led these materials to many uses such as drug delivery and artificial muscles. The increasing use of these materials has led researchers to continue research in the field of modeling ferrogels. Due to the porous nature of ferrogels, the ability to absorb a lot of liquid and their large deformations in the magnetic field, modeling of...

Exploring Auxetic Metamaterials by Changing the Geometrical Parameters

, M.Sc. Thesis Sharif University of Technology Ashouri, Amir (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

The properties of metamaterials can be tailored through modification of their microstructures geometry. In this regard, a vast range of metamaterials have been designed. Auxetic metamaterials are a novel class of materials exhibiting the interesting characteristic of negative Poisson’s ratio. Theoretically, auxetic metamaterials have improved mechanical properties such as shear modulus and fracture toughness. The design and modeling of auxetic metamaterials is not completed yet. In order to exploit the interesting properties of auxetic metamaterials, their potential applications have been investigated in medical, sports, automobile and defense industries, so far. In the present work, the...

Swelling and Temperature Increase Modelling of Ionized Porous Hydrogels for Solar Vapor Generation using FEM

, M.Sc. Thesis Sharif University of Technology Simyarian, Mahdi (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

The concern of water shortage in the past years has caused special attention to advanced water purification technologies. Using solar steam generators to separate water from impurities has made us use both renewable solar energy and provide potable water. For solar radiation, the maximum steam production capacity is theoretically 0.7kg/(m^2 h), which is a small amount. To increase this capacity, advanced materials and structure design are needed to improve the heat capacity of the converter by reducing heat loss and better converting solar energy into heat energy. One of the advanced materials used to improve water purification efficiency is hydrogel containing metal nanoparticles. These...

Modeling of Thermotropic Swelling of Smart Microgels by Finite Element Method

, M.Sc. Thesis Sharif University of Technology Ghasemian, Hossein (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Microgels, three-dimensional networks belonging to the family of smart materials, exhibit significant structural changes in response to external stimuli such as temperature. The rapid deformation of microgels upon thermal stimulation makes them a promising alternative for various mechanisms. Despite the similarities between hydrogels and microgels, many of their properties differ. Moreover, the Flory-Rehner model, typically used to describe the swelling behavior of temperature-sensitive hydrogels, only provides a qualitative description of microgel swelling. Nevertheless, previous numerical models of microgels have largely been based on the assumption that their behavior mirrors that of...

Theoretical and Computational Investigation of Quantum Plasmonic Properties of Nanocluster Dimers

, M.Sc. Thesis Sharif University of Technology Mahmoudi, Erfan (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon...

Theoretical Investigation of Ab-initio MD Approach to Increase the Efficiency and Accuracy of VCD Spectrum Calculation

, M.Sc. Thesis Sharif University of Technology Hadi, Hossein (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

Understanding of the Molecules is the main purpose of the chemistry. Ab-initio molecular dynamics (AIMD) as a branch of the computational chemistry, tries to give us a deep comprehension of the molecule, and its chemical, physical and optical activities. This comprehension, relies on the accuracy of quantum mechanics, in addition to the speed of the classical mechanics. The mixing of the quantum mechanics and the classical mechanics could simulate activities of the atoms in the time-domain, provided the mixing is done with precaution. This, in turn, helps us to forecast the response of a molecule in different situations, and also translating the macroscopic phenomena in a nanoscopic...

Investigation of Plasmonic Excitation in Carbonic Nanostructures Within Near-IR

, M.Sc. Thesis Sharif University of Technology Madadi, Mahkam (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have...

Using Nonlinear Effects of Light for Optical Signal Processing

, M.Sc. Thesis Sharif University of Technology Shatery, Farshid (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the...

Using Simulation-Optimization Approach for Fire Station Location and Vehicle Assignment Problem: a Case Study in Tehran, Iran

, M.Sc. Thesis Sharif University of Technology Pirmohammadi, Ali (Author) ; Amini, Zahra (Supervisor)

Abstract

In this research, the problem of locating fire stations and allocating equipment has been studied and a simulation-optimization approach has been presented to solve the problem. The mathematical models of this research were developed based on the idea of the randomness of the covered demand and the maximum expected coverage model. In these models, the issue of non-availability of equipment to cover accidents, the random nature of accidents, various fire incidents and the equipment needed to cover them are considered. Two mathematical models with deterministic and non-deterministic approach with different scenarios for demand are proposed. The non-deterministic model is developed with the aim...

Introducing An Integrated Framework For Solving The Fleet Planning Problem Using A Simulation-Optimization Approach

, M.Sc. Thesis Sharif University of Technology Sahebi, Armin (Author) ; Amini, Zahra (Supervisor)

Abstract

One of the main concerns of industrial companies’ managers is providing an efficient logistics system. To achieve an efficient logistics system, the fleet planning problem is studied by many researchers in recent years. This problem consists of multiple sub-problems at three levels: operational, tactical, and strategic. These sub-problems are closely related to each other and need to be studied and addressed in an integrated manner. In this research, an attempt is made to provide an integrated framework to solve the vehicle routing problem (operational), outsourcing problem (tactical), and fleet composition problem (strategic). These problems have various uncertainties, including customer...

Evaluation of Material Properties of Short Carbon Nanotube-Based Composites Using Nonlocal ElasticityTheory

, M.Sc. Thesis Sharif University of Technology Amelirad, Omid (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Classical theory of elasticity, which is founded upon results of mechanical experiments on the large scale materials, has reasonable results in predicting mechanical properties. The basic idea in this theory is that stress at a point of the material is only a function of the local strain and it is independent of the nonlocal strains. Therefore, the size of the material does not play any role in analyzing mechanical behavior of materials using this theory. However, results from experiments and atomic simulations have shown that in nano scale materials, such as carbon nanotubes (CNTs) and their composites, mechanical properties are strongly dependent on the size parameters of these materials....

Constitutive Modeling of Nonlinear Tumor Growth; A Finite Element Approach

, M.Sc. Thesis Sharif University of Technology Hosseinalizadeh, Mohammad (Author) ; Naghdabadi, Reza (Supervisor)

Abstract

Mechanical forces play a crucial role in tumor patho-physiology. Compression of cancer cells inhibits their proliferation rate and induces apoptosis. Additionally, compression of intratumor blood vessels has negative impacts on drug delivery system. Despite the great importance of the mechanical forces on the pathology of cancer, there are limited studies on the constitutive modeling of tumors. In this study, first, the tumor growth inside a rigid cylinder with an exponential growth function is represented, a model mimicking the growth of ductal carcinoma. Then, a mathematical model of a spherical tumor growth with a Gompertz growth function is represented. Using the notion of multiple...

Analytical Modelling and Optimization of Disk Type, Slot Less Resolver

, M.Sc. Thesis Sharif University of Technology Moheyseni, Atefeh (Author) ; Nasiri Gheidari, Zahra (Supervisor)

Abstract

Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate...